The use of optical fibers as a medium for transmission of digital data (including voice, internet and IP video data) is becoming increasingly more common due to the high reliability and large bandwidth available with optical transmission systems. Fundamental to these systems are optical subassemblies for transmitting and/or receiving optical signals.
A common optical subassembly comprises an interposer integrated with an optical component, such as an opto electric device or a photonics integrated circuit (IC). As used herein, an interposer functions as a substrate for optical, opto-electrical, and electrical components and provides interconnections to optically and/or electrically interconnect the optical/opto-electrical/electrical components. A typical interposer may comprise a substrate comprising, for example, silicon, having one or more grooves formed therein for holding fibers precisely. A conventional groove is formed in the shape of a “V” by wet etching the substrate to include two sidewalls that retain the optical fiber along its length. Wet etching a crystalline material such as silicon results in a predictable and very precise etch along the crystalline planes of the material. For example, silicon has a crystalline plane at 54.7°, thus, the sidewalls and the end facet of a wet etched groove are formed at a precise angle of 54.7° from the reference surface.
The end facet of a conventional interposer V-groove can be metalized so that it may be used as a mirror to reflect light between the optical/opto-electrical component and the optical fiber retained in the V-groove. For example, an opto-electrical light source, which has been flip-chip mounted onto the interposer, emits a cone-shaped light beam onto the V-groove end facet mirror. The V-groove end facet mirror reflects the light through an end of the optical fiber retained in the V-groove.
As discussed above, the surface of a wet-etched V-groove end facet is at an angle of precisely 54.7° from the reference surface. As such, light is reflected off the groove end facet mirror through the optical fiber at approximately −19.4° from the reference surface and also from the longitudinal axis of the optical fiber retained in the V-groove. Therefore, current devices utilizing the end facet mirror of the V-groove to launch light through an end of the optical fiber cause much of the light to be reflected away from the axis of the optical fiber resulting in non-optimal signal transmission performance.
Applicant recognizes that there is a need for an improved optical coupling between the optical component and the optical fiber conduit. In particular, Applicant identifies the need for an interposer that can be prepared using high-volume, economical manufacturing techniques. The present invention fulfills this need among others.